FIG. 7 is a diagram illustrating a basic operation of hearing aid processing. The upper spectrum in FIG. 7 represents a waveform of a signal before the hearing aid processing. The lower spectrum in FIG. 7 represents a waveform of the signal of the upper spectrum in FIG. 7 subjected to the hearing aid processing. In other words, the basic operation of the hearing aid processing amplifies amplitudes of signals having small amplitudes and maintains the amplitudes of signals having large amplitudes. The hearing aid processing thus compensates for the sense of hearing of people who have narrowed dynamic ranges for perception of sounds (or normally hear loud sounds but do not hear small sounds).
Techniques in application to television have been developed which provide contents in such a manner that listeners who need hearing aid processing (hereinafter, referred to as an elderly person) and listeners who do not need hearing aid processing (hereinafter, referred to as a healthy person) enjoy the contents together at the same time. For example, Patent Literature 1 discloses the following techniques.
According to a first technique, default sounds not subjected to the hearing aid processing are output from one (for example, left) speaker, and sounds subjected to hearing aid processing are output from the other (for example, right) speaker; thereby, sounds appropriately adjusted for elderly persons are provided from the right speaker.
According to a second technique, default sounds not subjected to the hearing aid processing are output from left and right speakers, and sounds subjected to the hearing aid processing are output from a highly directional speaker separately disposed; thereby, sounds appropriately adjusted for elderly persons are provided from the highly directional speaker.
According to a third technique, default sounds not subjected to the hearing aid processing are output from left and right speakers, and sounds subjected to the hearing aid processing are output from a headphone; thereby, sounds appropriately adjusted for elderly persons are provided from the headphone.